1. Technical Field
This invention relates generally to mobile navigational systems, and more particularly to a method and apparatus for displaying real-time graphical descriptions of navigational elements on a mobile computational device to assist a user in navigation.
2. Background Art
Navigational systems are becoming more and more popular. Gone are the days of traveling with only the guidance of the stars. Today's traveler has access to sophisticated navigational equipment to help them journey from point A to point B. These systems, be they mounted in a vehicle or simply in a handheld device, employ sophisticated electronics like global positioning system (GPS) sensors to tell travelers who are unfamiliar with the local geography not only exactly where they are, but also how to get from a starting point to a destination point. Additionally, some navigational systems are capable of providing a driver with a visual map.
Prior art navigational systems typically operate as follows: The navigational unit generally has an interactive visual screen or buttons that allows a driver to enter a desired destination location. The navigation unit then turns to a memory or CD drive that keeps map data. A local computer processor generates textual directions (e.g., “Drive for one mile and then turn right . . . ”, etc.) based on the map data and desired destination, and displays these directions, in addition to present latitude and longitude coordinates, on the screen.
These “self-contained” navigational systems require large, expensive memories and processors having local map data and map generation capabilities. Such memories and processors are often prohibitively expensive. Another problem with these systems relates to their textual output. A driver who takes the time to read a statement like “ . . . . Continue along Peachtree Street for 2.4 miles and then bear left onto Piedmont Road for 0.34 miles . . . ” runs the risk of diverting attention from the road, thereby risking having an accident.
Two recent developments in the field of navigational devices attempt to address these issues. The first improvement is that of server-based, networked navigational units. A server-based navigation system typically downloads map information to a navigation unit by a wireless communication, thereby eliminating the need to store detailed map information locally.
The second is that of using pictures instead of textual direction statements. For example, U.S. Pat. No. 6,182,010, issued to Berstis for example, teaches using a photographic image taken by a digital camera to represent given locations, like intersections for instance. Rather than displaying several lines of text on a screen, a digital image, either locally stored or downloaded from a server, is displayed on a screen. The prior art suggests that by downloading photographic images, the problems of large local memories and textual readouts may be eliminated.
Problems still remain with these prior art systems, however. The first problem with a photo image, downloading system is that photographic image files are quite large in size. Consequently, the local unit must still be capable of storing multiple, large images to properly update the screen. Additionally, this large amount of downloaded information may conflict with available transmission bandwidth, thereby slowing down the delivery of critical information. (Who wants to miss a turn because the unit is trying to download a large image file?) Finally, such systems still require excessive computations to be done by the navigation unit, increasing the complexity and cost of the navigation unit.
There is a need to reduce the computation complexity in a navigation unit. Reducing the computational complexity of the navigation unit reduces the cost of electronics required to perform vehicle navigation. Additionally, there is a need to decrease or minimize the amount of data transmitted to a navigation unit. Decreasing or minimizing the amount of data transmitted to the navigation unit allows the unit to respond quicker and reduces data usage and cost for the wireless communications. There is thus a need for an improved method and apparatus for generating real-time, graphical descriptions of navigational elements to aid a user in reading information from a navigational unit.